Fetal and Neonatal Brain Conditions
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Magnetic Resonance Imaging (MRI), particularly T2-weighted (T2w) and diffusion MRI (dMRI), plays a crucial role in the investigation of a wide range of fetal and neonatal brain conditions. This section details some of these conditions.

Fetal Conditions 
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**1. Congenital Brain Malformations**

- *T2w*: Detects structural abnormalities such as: Neural tube defects (e.g., Chiari II malformation), Holoprosencephaly, Agenesis of the corpus callosum, and Posterior fossa anomalies (e.g., Dandy-Walker malformation)
- *dMRI*: Used in research to assess white matter tract development (e.g., in callosal agenesis)

**2. Ventriculomegaly & Hydrocephalus**

- *T2w*: Assesses ventricular size and underlying causes (e.g., aqueductal stenosis)
- *dMRI*: Investigational use in detecting associated white matter injuries

**3. Fetal Ischemia/Stroke**

- *T2w*: Shows chronic lesions (e.g., porencephaly, cystic encephalomalacia)
- *dMRI*: May detect acute/subacute ischemic injury (restricted diffusion)

**4. Infections (TORCH: CMV, Toxoplasmosis)**

- *T2w*: Detects ventriculomegaly, polymicrogyria, calcifications
- *dMRI*: Rarely used but may show cytotoxic edema in acute infection

**5. Twin Complications (TTTS)**

- *T2w*: Identifies brain injury (atrophy, hemorrhage) in donor/recipient twin
- *dMRI*: May reveal acute ischemia


Neonatal Conditions
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**1. Hypoxic-Ischemic Encephalopathy (HIE)**

- *T2w*: Shows later-phase changes (edema, atrophy, cystic changes)
- *dMRI*: Detects early injury (restricted diffusion in basal ganglia, thalamus, white matter)

**2. Neonatal Stroke (Arterial/Venous)**

- *T2w*: Maps infarct territory and excludes hemorrhage
- *dMRI*: Identifies acute infarcts (bright DWI, dark ADC)

**3. Periventricular Leukomalacia (PVL)**

- *T2w*: Shows cystic changes and gliosis in chronic stages
- *dMRI*: Early detection of white matter injury in preterm infants

**4. Intraventricular Hemorrhage (IVH) & Post-Hemorrhagic Hydrocephalus**

- *T2w*: Depicts hemorrhage, ventricular enlargement
- *dMRI*: Detects periventricular injury in severe cases

**5. Kernicterus (Bilirubin Encephalopathy)**

- *T2w*: Hyperintensity in globus pallidus/subthalamic nuclei
- *dMRI*: May show restricted diffusion in acute cases

**6. Metabolic Disorders (e.g., MSUD, Mitochondrial Disease)**

- *T2w*: Shows delayed myelination and basal ganglia signal abnormalities
- *dMRI*: Detects cytotoxic edema during crises

**7. Neonatal Seizures (Etiology Evaluation)**

- *T2w*: Reveals structural anomalies (e.g., dysplasia)
- *dMRI*: Identifies ischemic/metabolic causes


**8. Hypomyelination Disorders**

- *T2w*: Excessively bright white matter (lack of myelination)
- *dMRI*: Assesses microstructural development and tract integrity
